Abstract

A common pathway for P-recovery from wastewater is phosphate precipitation as calcium phosphates. In this paper, a thermodynamic
model for phosphate precipitation is proposed based on various models of activity coefficients taking into account various calcium phosphate
phases which can crystallize in the range of pH to be considered, i.e. both dicalcium phosphate dihydrate (DCPD) and amorphous calcium
phosphate (ACP) for pH lower than 7.3 and only ACP for pH higher than 7.3. The parameters include the solubility products of ACP
and DCPD species. The observed discrepancy in liquid phase equilibrium constants reported in the literature leads to determination of an
uncertainty zone describing the precipitation domain. The results obtained offer interesting possibilities for a further optimization of process
operating conditions, i.e. determining Ca/P molar ratio, in order to reduce effluent pH (thus avoiding post-treatment) and, consequently, to
maximize reactor efficiency

Item Type:

Article

Additional Information:

Thanks to Elsevier editor. The definitive version is available at http://www.sciencedirect.com The original PDF of the article can be found at Biochemical Engineering Journal website : http://www.sciencedirect.com/science/journal/1369703X